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• 2.05.6 <br />(3) Protection of Hydrologic Balance <br />(a)(i) The applicant has prepared a drainage and sediment control system which <br />will minimize changes to the surface water and to the prevailing hydrologic <br />balance in the facilities area by detaining run-off in sediment ponds or <br />treating runoff with alternative sedimentation control. The sediment ponds <br />are designed to contain the run-off from the 10 year precipitation event. The <br />sedimentation control plan is presented in Volume III Exhibit 8, and on Maps <br />20, 21-1; 21-2; 21 '3,,,,m = , 22 ~6, 22-C;'22J 22K,?3,35 36;;,-36a and ,VotrSme <br />IV. <br />There is very little if any beneficial use made of surface run-off from the <br />ephemeral drainages in the permit and adjacent areas. These ephemeral <br />drainages typically only flow during spring snowmelt and significant <br />precipitation events. Sediment ponds B & C should alleviate the problem of <br />the ditches (Deer Trail Ditch & Fire Mountain Canal) plugging with sediment <br />and/or completely washing out do to previously uncontrolled runoff events. <br />The construction of mine entries, ventilation shafts and the mining of the <br />coal could cause water to move from formations above the coal seam into <br />• the mine. This potential water migration would be magnified by roof collapse <br />and fracturing caused by subsidence. Although the permeability of the coal <br />seam and surrounding strata is !ow and the quantity of water stored in the <br />formation is also low, some water will occasionally seep into the mine. <br />The Freeman Gulch vent shaft will be raise bored to an S-foot diameter. The <br />shaft will be lined with a 6-foot diameter steel casing. The steel casing will <br />be grouted through the water bearing zone which is approximately 0 to 140 <br />feet deep. The grout liner through this zone will we approximately 1-foot <br />thick. To prevent surface drainage from entering the shaft, the steel liner will <br />be extended at least 3-feet above the ground surface (see Map 35). A <br />screen will be placed on the top of the steel liner. <br />The quality of ground water that comes in contact with coal seams and <br />surrounding strata is generally degraded. Bear Coal Company prepared a <br />study of the potential effects of mining on the B-Seam aquifer (J. E. Stover <br />& Associates letter to DMG dated October 23, 1995). A correlation was <br />made between the geochemical characteristics of the roof, coal and <br />interburden and the degradation of the quality of water in the coal seam. <br />Soluble calcium, magnesium and sodium appears to degrade the quality of <br />ground water that comes in contact with the disturbed coal seam and <br />surrounding strata. This degradation of ground water quality is considered <br />typical for water which seeps into the mines in the Paonia Somerset area <br />PR-06 <br />2.05 - 67 - o~iot <br />AOPRovcq <br />~~15/02 <br />